update capsule build node version

[leightkt]

Description

updates node build version for capsule to 18
and fix sepolia chain id in demo button

PLEASE NOTE- Checklist must be complete prior to review.

Checklist

• Increment the version field in package.json of the package you have made changes in following semantic versioning and using alpha release tagging
• Check the box that allows repo maintainers to update this PR
• Test locally to make sure this feature/fix works
• Run yarn check-all to confirm there are not any associated errors
• Confirm this PR passes Circle CI checks
• Add or update relevant information in the documentation

Docs Checklist

• Include a screenshot of any changes (see docs README on running locally)
• Add/update the appropriate package README (if applicable)
• Add/update the related module in the docs demo (if applicable)
• Add/update the related package in the docs/package.json file (if applicable)

If this PR includes changes to add an injected wallet or SDK wallet module:

Please complete the following using the internal demo package.
To run this demo use the command yarn && yarn dev to get the project running at http://localhost:8080/

Tests with demo app (injected)

• send transaction
• switch chains
• sign message
• sign typed message
• disconnect

Tests with demo app (SDK)

• send transaction
• switch chains
• sign message
• sign typed message
• disconnect